Glycidol is an important raw material raw for polyglycerin, glycerol ester, dihydroxy propylamine, UV curing agent for perfumery and cosmetics, a detergent, drugs, a coating and semiconductors. Glycidol has been synthesized industrially by a method including oxidizing allyl alcohol by using hydrogen peroxide in the presence of a catalyst and a method including treating chloropropanediol with a base. However, although the above methods provide high production yield, these process suffer from the drawbacks such as 1) multistep synthesis which decreases the synthetic efficiency as well as increases the production cost and 2) produce large amount of waste water and salt.
Another method for preparing glycidol includes carrying out thermal decomposition of glycerol carbonate obtained from glycerol, as shown in following reaction.
    Thermal decomposition of glycerol carbonate is catalyzed by a metal salt catalyst and produce glycidol and carbon dioxide.    Glycerol is a renewable and cheap raw material, which is coproduced from bio-diesel production from vegetable oil or animal fat. These days, the increasing demand for biodiesel resulted in the byproduct glycerol available in large quantities at low price. Accordingly, synthesis of Glycidol from the glycerol carbonate which can be made from glycerol is worthy to be developed in the aspect of cost-efficiency and eco-friendly characteristics.
Meanwhile, as a method for preparing glycerol carbonate that is an intermediate from glycerol, there has been known a method using CO2, dimethyl carbonate, urea, or the like. In the case of a method that uses urea, it has high cost-efficiency and provides glycerol carbonate with relatively high yield. Japanese Laid-open Patent No. 2008-285457 discloses a method for preparing glycerol carbonate by using anhydride, such as MnSO4. Japanese Laid-open Patent No. 2007-039347 discloses a method for preparing glycerol carbonate by using MgSO4 as catalyst. In addition, U.S. Pat. No. 6,025,504 discloses use of a sulfide of Mn, Mg, Fe, Ni or Cd as catalyst, and Korean Patent Publication No. 1307559 discloses a method for preparing glycerol carbonate by reacting glycerol with urea in the presence of a Zn catalyst coordinated with halide-based and nitrate-based ligands. The above-mentioned documents disclose methods for preparing glycerol carbonate based on urea. However, there is no description about a method for preparing glycidol starting from the produced glycerol carbonate.
Meanwhile, Japanese Laid-open Patent Nos. 2009-137938 and 2009-067689 disclose a method that includes preparing glycerol carbonate by using a Lewis acid catalyst, such as ZnSO4. Then, the product was distilled using thin film distillation unit at 150-180° C. under 0.06-0.7 kPa for the removal of zinc catalyst, a Lewis acid, which functions as catalyst during the the decarboxylation of glycerol carbonate for the synthesis of glycidol. Actually, many documents report that a catalyst having a Lewis base type anion is used as catalyst for decarboxylation of glycerol carbonate.
U.S. Pat. No. 2,856,413 discloses a method that uses a phosphate or carbonate base compound. U.S. Pat. Nos. 5,359,094 and 7,888,517 disclose a method that uses a sulfate, halide or acetate compound. In addition, use of ionic liquid-based nitrate is disclosed in Journal of Catalysis 297, (2013), 248-225. The above-mentioned anionic or Lewis base-type catalysts lose their anionic characteristics through acid-base reaction when a Lewis acid is present in the reaction mixture, resulting in loss of catalytic activity.
Therefore, in the reaction of preparing glycidol from glycerol by way of glycerol carbonate, it is important to remove the catalyst used for the preceding reaction or to purify glycerol carbonate through distillation or the like.
A typical method for removing a catalyst for use in preparing glycerol carbonate includes the above-mentioned thin layer distillation method. Although the thin layer distillation method is useful for overcoming the high boiling point of glycerol carbonate and thermal unstability thereof, it requires a high distillation temperature and a high vacuum degree, leading to high energy consumption and increased cost of equipment in a process for preparing glycidol.
As a result, there has been a need for a method for preparing glycidol from glycerol by a simple process, while reducing energy consumption and cost of equipment.